1. Field of the Invention
The present invention relates to a conductor detecting device. More specifically, the invention relates to a conductor detecting device which has a simple structure and can reduce erroneous operations.
2. Description of the Related Art
A gearbox accommodating gears is filled with a lubricating oil. When the gears are driven, the gears in mesh produce fine particles or fragments as metal powder or metal shards, which are mingled in the lubricating oil.
A bearing box which accommodates a bearing is also filled with the lubricating oil. When a shaft is driven, fine particles or fragments are produced as metal powder or metal shards from the sliding surfaces of the bearing and the shaft and are mingled in the lubricating oil.
The fine particles or fragments of the gears may be caught by the normal gears or clog a lubricating oil passage in the bear box, causing an adverse effect. And, when the abrasion or damage of the bearing proceeds, the drive of the shaft is adversely affected.
Therefore, detection of the metal powder or metal shards mingled in the lubricating oil enables to judge whether a level of abrasion or damage of the gears or bearing has exceeded a prescribed level.
The gears and bearing are made of metal and are conductors. Accordingly, the gearbox or the bearing box is provided with a metal detecting device for detecting a conductor such as metal powder, metal shards or the like produced due to abrasion or chipping out of the gears or bearing.
FIG. 7 is a diagram showing a structure of a conventional metal detecting device 72 which is disposed in a gearbox.
The metal detecting device 72 is provided with a detecting section 71. The detecting section 71 is provided with two magnets 70a, 70b, which attract metal powder or metal shard M and are disposed with a space between them so to be electrically insulated. In the detection section 71, electric current Ix, which indicates the detection of the metal powder or metal shard M, flows through a circuit when the magnets are electrically connected by the metal powder or metal shard M which is attracted by the two magnets 70a, 70b. The current Ix is directly converted into a warning signal and output or processed as accumulated data, output warning signal or the like by an unshown controller. When the warning signal is output, it can be judged that the abrasion or damage of the gears has exceeded a prescribed level.
When machining to produce the gears, swarf is produced. The swarf often stays on the gear surface even if the gear surface is washed. The swarf adhered to the gear surface is mingled into the lubricating oil.
Furthermore, when the gearbox is being machined, cuttings are produced as metal powder or metal shards. Such cuttings might remain adhered to the inside surface of the gearbox even if the gearbox interior is washed. Therefore, the cuttings adhered to the inside surface of the gearbox are also mingled into the lubricating oil.
There is also a possibility that when the gears are being checked for maintenance, a metal foreign material, which is different from the fine particles or fragments of the gears, is externally mingled into the lubricating oil in the gearbox.
Here, the fine particles or fragments of the gears are attracted by the magnets 70a, 70b so to electrically connect the magnets, so that the current Ix flows, and the warning signal is output.
But, the metal detecting device 72 is provided with only one detecting section 71, so that the current Ix flows and the warning signal is output when the swarf, cuttings or metal foreign material is attracted to the magnets 70a, 70b to electrically connect the magnets.
Thus, the metal detecting device 72 had an erroneous operation that a warning signal was output because the current Ix flows when swarf, cuttings or metal foreign material, which is mingled in the same manner as the fine particles or fragments of the gears, is attracted by the magnets 70a, 70b to electrically connect the magnets.
For example, Japanese Utility Model Laid-Open Publication No. SHO61-3466 discloses a metal detecting device which is provided with a plurality of detecting sections.
FIG. 8 is a diagram showing the metal detecting device described in Japanese Utility Model Laid-Open Publication No. SHO61-3466.
Metal detecting device 83 of FIG. 8 is configured to have a parallel circuit 82 by disposing a plurality of detecting sections (magnet devices) 81, each of which has two magnets 80a, 80b disposed with a space between them to attract metal (magnetic foreign material). According to this metal detecting device 83, when metal is attracted to any one of the plural detecting sections 81, 81, . . . , the parallel circuit 82 is brought into conduction, and a current indicating the detection of metal flows through the circuit.
The metal detecting device 83 of FIG. 8 is configured to improve its reliability of metal detection by disposing the plural detecting sections 81. Therefore, according to this conventional metal detecting device 83, the swarf, cuttings or metal foreign material, which is mingled in the same manner as the fine particles or fragments of the gears, is detected without fail. Thus, the problem of causing an erroneous operation remains unsolved.
For example, the conventional metal detecting device 83 can remedy an erroneous operation by incorporating a logical circuit or performing a judging process by inputting output signals of the plural detecting sections 81, 81, . . . , to the controller and, when metal is detected by any one of the plural detecting sections 81, 81, . . . , judging that metal is not detected, and when metal is detected by two or more detecting sections 81, 81, . . . , judging that metal is detected.
But, addition of the controller to a conventional metal sensor has a disadvantage that the structure become complex and the cost becomes high.
The present invention has been achieved under the above circumstances, and it is an object of the invention to reduce an erroneous operation by a simple structure.
To achieve the above object, a first aspect of the invention is directed to a conductor detecting device which detects conductors by attracting the conductors to a plurality of magnets, wherein three or more magnets are disposed with spaces between the respective magnets to configure a series circuit; and the conductors are attracted by the three or more magnets so to be electrically connected between the respective magnets to bring the series circuit into conduction, and an electric signal indicating the detection of the conductors is output.
The first aspect of the invention will be described with reference to FIG. 1.
According to the first aspect of the invention, when two or more conductors M1, M2, M3 (three conductors in FIG. 1) are attracted to three or more magnets 1a, 1b, 1c, 1d (four magnets in FIG. 1), the conductors M1, M2, M3 are electrically connected between the respective magnets, and a series circuit 3 is brought into conduction to cause a current Is to flow. Thus, an electric signal (voltage Vs (=V) indicating the detection of the conductors M1, M2, M3 is output.
According to the first aspect of the invention, when two or more conductors are attracted between the three or ore magnets, the series circuit 3 is brought into conduction for the first time to output the electric signal Vs (=V). Therefore, when only one of the mingled swarf, cuttings or metal foreign material is attracted between the magnets, the electric signal Vs (=V) is not output, and when two or more metals are attracted between three or more magnets, the electric signal Is is output, so that an erroneous operation due to the attraction of one foreign material or the line is not caused.
By disposing the three or more magnets 1a, 1b, 1c, 1d with a space between them to configure the series circuit 3, an erroneous operation can be prevented, and addition of a controller to a metal sensor is not needed unlike a conventional art, so that the structure can be made simple, and the cost can be reduced.
A second aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged around the outer periphery of a rod member.
The second aspect of the invention will be described with reference to FIG. 2.
According to the second aspect of the invention, the three or more magnets 1a, 1b, 1c, 1d are arranged around the outer periphery of the rod member 20.
A third aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged concentrically.
The third aspect of the invention will be described with reference to FIGS. 4(a), (b).
According to the third aspect of the invention, three or more magnets 40a, 40b, 40c are arranged concentrically.
A fourth aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged in a circumferential direction.
The fourth aspect of the invention will be described with reference to FIG. 5.
According to the fourth aspect of the invention, three or more magnets 50a, 50b, 50d, 50d are arranged in a circumferential direction.
A fifth aspect of the invention relates to the first aspect of the invention, wherein the three or more magnets are arranged in parallel.
The fifth aspect of the invention will be described with reference to FIG. 6.
According to the fifth aspect of the invention, three or more magnets 60a, 60b, 60c are arranged in parallel.